Optical communication networks are widely used for providing various types of communication services to clients. The part of the network that is directly connected to the clients is often referred to as an access network. The part of the network that carries traffic over larger distances is often referred to as a transport or backbone network. In many communication networks, access to clients is provided using protocols such as Gigabit Ethernet (GbE), 10 GbE, future 40 GbE and 100 GbE, Synchronous Optical Networking (SONET)/Synchronous Digital Hierarchy (SDH) and Fibre Channel (FC).
In some transport networks, multi-Gigabit traffic is transported using Optical Transport Network (OTN) protocols. The OTN technology is described by the International Telecommunication Union (ITU) in ITU-T Recommendation G.709/Y.1331, entitled “Interfaces for the Optical Transport Network (OTN),” March, 2003, which is incorporated herein by reference, as well as in subsequent amendments and drafts of this recommendation.
The ITU-T G.709/Y.1331 recommendation and its subsequent drafts define Optical channel Data Units (ODUs) of different classes, each characterized by a certain data rate. For example, ODU classes denoted ODU0, ODU1, ODU2/2e/1e, ODU3 and ODU4 are specified to carry traffic at 1 Gbps, 2.5 Gbps, 10 Gbps, 40 Gbps and 100 Gbps rates, respectively. ODUs are mapped to Optical channel Transport Units (OTUs), which are then sent over the transport network. Each OTU may carry a single ODU or multiple ODUs.